1. Field of the Invention
The present invention relates to a defibrillator with an electrocardiographic monitor which displays and records electrocardiographic signals, or performs data processing by amplifying electrocardiographic signals induced at electrodes by means of a preamplifier and then supplying the signals to an electrocardiographic signal processing circuit through high-pass filters.
In such a defibrillator with an electrocardiogram monitor, when the defibrillator is operated, a polarization voltage greater than an ordinary signal level is generated between electrodes as a result of the application of a high voltage. Therefore, an electrocardiograph is provided with an instantaneous switch for grounding an output end of a coupling capacitor which forms a high-pass filter when a high level signal, as well as such polarization voltage, is instantaneously input at the time of electrode switching or the like. This instantaneous switch prevents the scale-over of an abnormally high level signal in an output unit.
However, there are some cases in which the amplitude of the above-mentioned polarization voltage at high voltage application time reaches approximately .+-.300 mV and then gradually decreases in 10 seconds or thereabouts. If the instantaneous switch is operated to prevent the scale-over or the like, electrocardiographic signals are completely vanished.